Lithium cell with internal automatic safety controls

ABSTRACT

An electric cell with a lithium/sulphur-dioxide electrolyte complex, corrosive and potentially dangerous, and having automatic protective structural features responsive to excessive internal temperatures or pressures that would be due to internal fault conditions or to external short-circuit conditions, with those protective features serving to selectively vent the cell or to break the internal cell circuit, to prevent explosive rupture of the cell and consequent possible damage to personnel in the adjacent surrounding environment by the corrosive ingredients of the cell.

This invention relates to an electric energy cell, particularly of thelithium/sulphur dioxide type.

In many military and civilian applications, batteries are required toserve as standby energy sources in many environments where thetemperature may drop to values as low as minus 60° F. At suchtemperatures, the ordinary conventional cell loses its ability tofunction properly and normally and therefore becomes useless.

Consideration has recently been given to a new type of primary cellutilizing a lithium/sulphur dioxide combination because of the unusualhigh quality operation over an extremely wide range of temperatures,particularly from a low temperature of minus 60° F to a normally usualambient temperature.

There are many problems involved where lithium is used in a batterycell. Lithium itself is highly chemically active and reacts with manyother elements, and, particularly, reacts explosively with water, or inthe presence of moisture.

A primary electric cell of almost any type is generally hermeticallysealed, in order to prevent leakage and to prevent access of moisture orany other foreign matter to the cell, since such leakage or such accesscould affect the predesigned operation of the cell and could lead to itsdeterioration. Where lithium is used in a cell, its potential of highactivity, where not properly controlled, makes a hermetic sealimperative. Moreover, not only the final hermetic seal, but all themanufacturing processes in forming the cell before the hermetic seal isapplied, must be restrictively controlled and safeguarded so that nomoisture is permitted to enter into the cell, either during manufactureor after the cell container is closed and sealed.

In order to provide for proper cell operation with an adequate quantityof the sulphur dioxide gas, in an appropriately limited volumetricspace, according to the cell dimensions, the gas must necessarily beunder pressure, which under normal conditions and room temperature maystabilize at about 50 lbs. per square inch. Upon the evolution of heatwithin the cell, the pressure may rise within a relatively short time to150 lbs. per square inch, or, in aggravated conditions, even to apressure as high as 300 lbs. per square inch and cause explosion of thecell.

Several conditions that would generate excessive heat in the cell mightcause such an excessive internal pressure. Internal or external shortcircuit conditions could do that.

An internal short circuit within the cell would generate heat whichcould remain internally concentrated and do damage before the heat couldbe conducted outward to an external surface to be dissipated, to preventthe development of a dangerous high internal pressure. An external shortcircuit on such a cell could cause a high internal resistance heatingloss, which could also lead to a dangerous high internal pressure.

Under such resulting conditions of internal high pressure, such a cellmight well rupture and explode, with a consequent force that would throwthe corrosive materials and toxic fumes of the cell through a sufficientdistance to possibly strike workers within a region near the cell. Ifsuch explosion should occur when the cell is in operation in a packagedassembly, it could occur in a confined region, or in a confiningcontainer, that might provide a possibly adequate safeguard againstprojectile injury to anyone present, but the fumes could still behazardous. Thus, a short-circuit condition on such a cell, eitherbecause of an internal short circuit within the cell, or while the cellis being used in other ways, in an open unconfined atmosphere, couldmake the cell an extremely dangerous and hazardous projector of thehighly reactive and corrosive materials, and of the toxic fumes of thecell.

Since pressure will be an end result of any troublesome conditions,including high temperature, whether within or outside of the cell, theexcessive pressure condition is relied upon as an indicator of trouble,and a pressureresponsive action is arranged to provide the safetycorrecting operation to prevent harmful effects. Thus, pressure responseis also essentially equivalent to temperature response.

One primary object of this invention is to prevent the development andaccumulation of dangerous high pressure within such a cell, and, forthat purpose, to provide some safeguard or safeguards which willselectively vent the cell when the internal atmospheric pressure of thecell becomes excessive.

Another important object of the invention is to provide what is ineffect an internal circuit breaker for the cell, as a safeguard againstan external short circuit condition that would generate a sudden highloss within the cell and that would create a rapid temperature rise andconsequent high pressure condition, beyond the heat-dissipating abilityof the cell.

In the cell of this invention, the selectively controlled ventingprevents the accumulation of high pressure within the cell, whilemaintaining a substantial seal to prevent ingress of ambient air, whichis an important feature of control.

To prevent the harmful effect within the cell that would result from anexternal short circuit in the cell, the cell is provided with aninternal structure that constitutes essentially a circuit breaker, thatoperates to open the internal electrical circuit of the cell toterminate delivery of energy to the external short circuit, wheninternal heat generates a high pressure reconized as potentiallydangerous.

Since a condition of high pressure within the cell is indicative of acondition likely to cause an explosive rupture of the cell, a suitablepressure-responsive element is provided in the cell construction topremit venting action to anticipate and thereby prevent an explosivepressure condition; and, also, a suitable pressure-responsive element isprovided to open the electric circuit of the cell.

Ordinarily, commercial cells of the dimensions of the -C- cell provide astructure in which a cylindrical can serves as an electrode termianal ofnegative polarity, and a central axial button, that is suitablyinsulatingly supported and sealed with respect to the container, isprovided to serve as a contact terminal of positive polarity to theexternal circuit.

As a further precaution in the case of the present cell, because of itsrelatively hazardous type of operation, the polarity of the electrodesare reversed, in order that cells of this design may not be randomlyassembled with ordinary conventional cells of similar dimensions.

At the present state of possible utility, it is contemplated that theuses of these hazardous cells will be limited to specifically militaryoperations, where, usually, many other safeguards are provided andcarefully supervised for the sources of energy that are employed.

An object of the invention is to provide a primary cell unit structureutilizing a lithium/sulphur dioxide complex with its extremely highenergy density content, and equipped with suitably protective featuresto ensure against possible explosive ruptures, that could be easilycaused by the usual operating conditions for a unit electric primarycell.

Another object of the invention is to provide an efficient structuralassembly which may be manufactured to assure the exclusion of moisturethat would be detrimental and dangerous within such a lithium/sulphurdioxide cell during operation.

Another object of the invention is to provide a simple and effectiveoperating structure in a lithium/sulphur dioxide electric cell whichwill embody and function as its own circuit breaker, internally withinthe cell, when external short-circuiting conditions would normallydictate such an operation between the cell as a source of power and theexternal circuit supplied thereby.

Another object of the invention is to provide a method of constructingand assembling such a lithium/sulphur dioxide cell to assure acompletely dry cell atmosphere, free of harmful moisture.

Another object of the invention is to provide a primary cell employing alithium/sulphur dioxide operation, with means for selectively ventingthe cell, gradually for gradually increasing excess internal atmosphericpressure, and quickly for rapidly venting in case of conditions likelyto lead to high pressure explosive conditions within the cell.

The details of construction and the method of assembling and forming thecell, and the manner in which the several elements cooperate to providethe desirable safety features, are all described in more detail in thefollowing specification, taken together with the drawings, in which

FIG. 1 is a vertical sectional view through a cell of the invention;

FIG. 2 is a top plan view of the cell;

FIG. 3 is a sectional view of the layered anode and cathode in planarassembly, before it is helically wound and disposed in the cellcontainer; and

FIG. 4 is a schematic view of the system for injecting an electrolyteinto an individual cell after the container has been dry sealed with theelectrode component elements inside the container.

This invention generally involves an electric cell utilizing a lithiumsalt and sulphur dioxide combination disposed in a container suitablysealed to exclude possibility of moisture entering the container, whichcould cause dangerous explosion, while at the same time protecting thecell against a type of operation that might produce dangerous explosionsby reason of the generation of excessive pressures within the cell; withprotective features that permit selective venting and internal circuitopening within the cell, when excessive pressure, or temperature, orcurrent, conditions occur in the cell.

Because of the special construction of the cell, and because of thespecial safeguards that must be taken in assembling a cell for safeoperation, the invention includes also a method of construction andassembling the cell to provide the essential safeguards to assure safeoperation.

FIG. 1 shows a vertical sectional view taken along the central verticalplane that shows the construction and assembly arrangement of the finalcell.

As shown in FIG. 1, a cell 10, in accordance with the invention,comprises an outer enclosing can 12, generally of initially hollowcylindrical form, provided with a bottom closure shown as a metal cup14, closely fitting internally within the outer can 12 and peripherallywelded thereto. The bottom metal cup 14 is distendable under pressurewhen in the cell, a condition that will be further discussed below, as afeature utilized as a safeguard.

The upper end of the can 12, originally open, is formed and shaped toprovide a re-entrant portion consisting of three parts, an annularshoulder end rest 18, an axially inwardly extending circular limitingwall neck portion 20, and a transverse annular seat 22. The annular seat22 serves to support a double layer sandwich 25, consisting of twolayers 24 and 26 as annular rings of insulating material, preferably ofan elastomer that will accept compression and retain its resilience inthe chemical environment of the cell materials.

The double layer sandwich 25, consisting of the two layers 24 and 26 ofinsulating material, normally fits snugly into the circular space withinthe circular neck 20 and rests snugly and under pressure on the annularseat 22, due to the compression force impressed by a final assemblypressure ring 28, whose outer peripheral border is anchored by weldingonto the annular reentrant shoulder end rest 18 of the upper end of thecontainer 12, at arcuately spaced spots 30, as shown in FIG. 2. As shownin FIG. 2, the annular pressure ring 28 is appropriately slotted toprovide a plurality of inwardly extending radial vent fingers 32 whichare supported and disposed in pre-stressed condition in order to impressa downward pressure force on the top layer 26 of the insulatingsupporting sandwich 25.

The insulating sandwich 25 serves to support a hollow cylindricalmetallic supporting shell 36, that has an external annular peripheralflange 40 which seats and nests between the two sandwich layers 24 and26 in order to be insulatingly supported by them. The metallicsupporting shell 36 is axially hollow and has an upper bore 42 to definean upper inner chamber at its upper open end, that communicates, at itslower end, with an extending passage 43A of lower and smaller bore 43within a coaxial extenion 46 of the shell body 36. The function of thesupporting shell 36 at its upper end is to support a plug seal 48, ofsuitable elastomeric material, to substantially fill and close the shellchamber 43. The plug seal 48 will later serve as a plug through which ahypodermic needle will be inserted through the sealing plug 48 forevacuating the container can 12 and for then conducting the electrolyteinto the cell for filling the evacuated space with the sulphur dioxidesolution that is to serve as the electrolyte for the cell.

In order to maintain the elastomeric seal plug 48 compressed for goodpressure engagement with the inner wall surface of shell 36, a pressureand retainer ring 50 is employed, which is dimensioned to fit with asnug pressure fit into the upper open end of the supporting shell 36, towhich the ring is then suitably bonded, as by brazing, with a materialsuch as Woods metal, which has a definite melting point at apredetermined temperature at which it is desired to permit the ring 50to be released from sealing bond with the shell 36. The melting point ofWoods metal at 170° Fahrenheit is enough above the normal safe operatingtemperature of 160°, to provide quick detection of a dangeroustemperature condition.

The tube 52 is spot welded to the depending bracket 46, as indicated bythe weld spot 53. The tube 52 has several functions. It is provided withone or more fillports 54, which are small openings drilled through thewall of the tube 52, to provide communication with the main chamber 56of the cell, that accommodates the working chemical components and theelectrolyte in general.

The tube 52 serves a primary function here as a stationary contactelement of a circuit breaker within the cell. The lower circular end 52Aof tube 52 serves as a stationary contact surface of such circuitbreaker, at which the circuit of the cell is opened to disconnect thecell from an external circuit.

The tube 52 also serves as a central axial spacer for the helicalwraparound 60 which includes the working electrodes of the cell.

In FIG. 3, the working electrodes are shown in assembly at anintermediate stage of assembly, with a lithium sheet 62 as the workinganode of the cell, and a sheet layer of carbonaceous mix 64 as cathodeseparated from the lithium by a perforated polypropylene barrier 66.

The lithium sheet 62 is 0.010 inch thick, impressed in and supported ona copper substrate 70, which may be perforated or of mesh structure. Thecarbonaceous cathode depolarizer mix 64 is about 0.030 inch thickbuttered on the aluminum substrate 68, also of perforated thin sheet ormesh structure. This layered assembly is provided with two tabs,electrically connected to the respective substrates. Tab 71 is connectedto the cathode 64, 68, and tab 72 is connected to the anode lithium andsubstrate 62, 70.

During manufacturing assembly of the cell, the planar assembly 60 iswrapped into helical form for axial insertion into the cam 12 from thebottom, to be slipped onto and over the center tube 52, into space 56.The copper tab 72 has been welded to a convenient area 14A, on thebottom closure cup 14. The other tab 71 is secured to an insulation disc74, which is secured to a central region of the bottom closure cup 14,to take advantage of the maximum axial movement and displacement of thatbottom closure cup when distended by excess pressure within the cell. Inthe initial dry assembling operation, the helical electrode assembly isthus physically connected to the bottom closure cup 14 as asub-assembly, which is then inserted into the can 12 to place theelectrode assembly in operating position in chamber 56, and to place theclosure cup in position to close the can bottom ready for welding andsealing. At the same time, the can bottom cup 14 is moved to properposition to place the depolarizer contact tab 71 of FIG. 3 into contactwith the bottom edge 52A of tube 52.

Normally, when the bottom end of the tube 52 engages the contact tab 71,the circuit through the cell is from the top safety cap 50 down throughthe metallic shell support 36, thence through the tube 52 down to andthrough the depolarizer contact tab 71 through the working cell elementsincluding cathode depolarizer 64, the electrolyte, and the anode 62 tothe anode tab 72, the bottom closure cup 14, and the can 12 to which theclosure cup is suitably sealed by welding.

The bottom of the tube 52 is kept in contact with the depolarizercontact tab 71 by the normal resilient pressure of the bottom cup 14,pressing upwardly through the insulator disc 74, which has beenappropriately secured to the inner surface of the can bottom cup 14.During normal operations the pressure in the cell is not high enough todistend the can bottom cup 14, and therefore the contact between thetube bottom 52A and the depolarizer contact tab 71 is highly conductiveand of minimum resistance, under the pressure of the bottom cup 14.

Upon the occurence of one of the undesirable conditions that results inan increased pressure within the can, that increase in pressure reactson the flexible bottom cup 14 of the can and causes the cup to distendoutward, as indicated by the dotted line 14A, and the outward distendedmovement of the bottom cup 14 moves the insulator and the depolarizercontact tab away from, and out of contact with, the bottom edge 52A ofthe tube 52. The cell circuit is thus interrupted at the bottom edge ofthe tube 52, to disconnect the operating elements of the cell from thetube 52, and, consequently, from the top outer safety cap 50, thatserves also as the terminal connected to the depolarizer cathodematerial during normal operation of the cell.

Even though the circuit of the cell is thus internally opened, so thatfurther operating cell current transfer is terminated, there may stillbe conditions within the cell that continue to generate heat that willraise the temperature within the cell and thus increase the pressure toan explosive value that could be dangerous to anyone within theproximity of the cell, if such pressure were permitted to continue toincrease. There are, thus, two conditions that are indicative of apossible dangerous explosion, namely, the temperature developed withinthe cell, and a possible resulting pressure.

If the pressure condition changes gradually, as might be caused by anormal loading of the cell, but without the occurrence of a necessarilyhazardous situation, adequate protection may be provided to the cell bymerely permitting and providing for slight venting. Upon the occurenceof conditions of that kind, the vapor pressure gas within the cell maypress against the under surfaces of the bottom sandwich layer 24, as atthe region indicated by the arrows 80, and then move out in thin gaslayer or strip form along the under surface of that bottom sandwichlayer 25, as for example, along a path indicated by the dotted line 82,up to the space 84 directly underneath the radially extending fingers32. Those fingers 32 are supported as cantilever beams at their rearregions, adjacent the weld points 30, so that the forward ends of thosecantilevered fingers 32 may rise slightly from the top surface of theupper sandwich layer 26, to permit a small bubble of the gas to exitfrom the cell and thereby relieve the pressure within the cellsufficiently to hold that pressure down below a dangerous pressure valuewithin the cell.

Thus, under normal operating conditions, where the cell is properlydoing the work for which it was intended, and the energy supplied by thecell is not creating a dangerously abnormal condition, simple occasionalventing, of a small amount of the electrolyte vapor as a gas, may besufficient to protect the cell from accumulating an excessive pressureinternally, and the operation of the cell may continue without danger orhazard to anyone in the environment of the cell.

If however, a condition develops within the cell, due to internal orexternal conditions, that causes a fast temperature rise, that wouldundoubtedly cause a subsequent pressure increase, the high thermalconductivity of the tube 52 and its supporting frame shell 36 areutilized to conduct the heat to the plug seal retaining ring 50, and tosoften the bonding material of that ring sufficiently to release thering from the shell 36. Consequently, pressure on the elastomeric plugseal material 42 is relieved to permit the compressed plug seal toexpand to full volume of its uncompressed condition, and, thereby, torelieve the pressure of that seal 42 on the inner wall surfaces of theshell 36, to permit the gases within the cell container to rush outquickly, through the openings or ports within the tube 52, and upthrough the central axial passage 44 into the internal chamber of thecell 36, past the relieved loose plug seal 42, and out through thedimple opening 51A, formed in the top of the seal safety cap 51 afterthe spot weld closure during manufacture.

Thus, on the occurrence of dangerous temperature, an immediate rise inpressure, or even in case of a delayed rise in pressure, the cell isable to control itself by the three provisions noted, namely, first, bythe switch opening as a circuit-breaker operation at the bottom of thetube 52, by the distention of the can botton 14; or, secondly, by theslow leakage along the path 82 up through and past the cantilever springfingers 32; or, thirdly, by the fast release of the gas pressure outthrough the top plug seal and safety cap, where the temperature riseindicates an extremely dangerous condition that is probably likely tolead to an explosion.

In manufacturing assembly, the elements of the cell are assembled inposition in the can, and the can is dry sealed, before the electrolyteis introduced, and the seal plug is compressed against the inner wall ofthe shell 36 and held in such compressed condition by the retainer ring50.

At this time, the elastomeric materials of the sandwich support 25 andof the seal plug 48 are tightly compressed against their adjacentcompression and supporting surfaces, to provide an adequate seal for thecell. The cell can is now ready to be filled with the electrolyte.

To accomplish the filling operation, a filling system is utilized suchas is shown in FIG. 4. A hypodermic needle 90 is thrust downward intoand through the full length of the seal plug 48, to extend down belowthe plug into the region of the depending portion 46 of the supportingshell 36, in order to couple the inner space of the cell intocommunication with a vacuum system 92, through a three-position valve94, which serves in one position to connect the cell to the vacuumsystem, and in the second position to connect the cell 10 to theelectrolyte supply 96, and in its third position to withdraw any excesselectrolyte from the needle before a subsequent filling operation.

After the hypodermic needle is inserted down into the cell space, thevalve 94 is moved to its position to connect the vacuum system to thecell, to evacuate the cell to a predetermined vacuum level, as well asto assure that the cell is free of any moisture. The cell is then readyto receive its charge of electrolyte.

The valve 94 is then moved to its filling position, at which theelectrolyte from the supply 96 is directed into the cell, in apredetermined premeasured quantity, as measured in a volumetricmeasuring device 98 to assure the introduction of a definite quantity ofthe electrolyte into the cell.

After the desired quantity of electrolyte is introduced into the cell,the excess electrolyte in the hypodermic needle 90 is withdrawn throughthe valve and a suitable vacuum pump 100, and returned to theelectrolyte supply to prevent contamination of the atmosphere.

The needle 90 is then completely withdrawn from the seal plug 48, andthe elastomeric characteristics of the seal plug 48 reclose the openingbehind the withdrawing needle, and reseal that opening, so the sealingaction of the plug continues to maintain the cell hermetically sealed,against admission of anything from the ambient atmosphere. At this time,the vapor pressure of the electrolyte within the cell is positive, sothat there is no tendency to draw any of the ambient atmosphere into thecell, during withdrawal of the hypodermic needle.

As indicated in FIG. 4, the cell is cooled, while being filled, to atemperature below minus 10° Centigrade, to help the electrolyte inliquid state. The apparatus schematically shows the cell held in a metalblock of high thermal conductivity, immersed in a bath maintained at thedesired low temperature.

In FIG. 5, the structure of the internal circuit breaker switch is shownin more detail.

The details of construction and the method of filling and assembly maybe variously modified without departing from the spirit and scope of theinvention as defined in the claims.

What is claimed is:
 1. A self-controlling electric primary cellconstructed to limit or prevent internal pressure likely to lead toexplosive rupture, said cell comprisinga. a container enclosure; b.anode means; c. cathode means comprising a depolarizer cathodic bodydisposed within the cell container; d. an electrolyte forelectrochemically relating said anode means and said cathode means togenerate an electric current between them for conduction to an externalcircuit; e. an outer electrode element disposed on the outside of saidcontainer; f. an electrical circuit conductor extending from saiddepolarizer body to said outer electrode element, said circuit conductorconsisting of a filling tube for introducing a fluid electrolytecomponent into the container can during manufacture, and wherein saidfilling tube serves as a stationary switch element; g. electricalswitching means disposed within said cell enclosure and responsive to anundesirable operating condition within the cell, which prevent theaggravation of said condition by opening the circuit between theelectrical circuit conductor, the depolarizer and the outer electrodeelement, wherein the undesirable condition is excessive pressure causedby excessive temperature and excessive current; h. said electricalswitching means including a movable switch element, which cooperateswith the stationary switch element and is controlled by said conditionwithin the container.
 2. A self-controlling electrical cell, as in claim1, in whichsaid container enclosure supports said movable switchelement; and said container enclosure embodies an element subject todifferential pressure, between internal cell pressure and externalambient pressure, for controlling the movable switch element.
 3. Aself-controlling electric cell, as in claim 1, in which said containerenclosure includesa. a seal between the inside of the container and theoutside atmosphere; b. means for holding said seal under closingcompression; and c. said seal-holding means includes apressure-responsive element, normally closed but responsive topredetermined excess atmospheric pressure in the container enclosure,for temporarily moving to pressure-relieving position to relieve andreduce excessive atmospheric pressure within the container enclosure. 4.A self-controlling electric cell, as in claim 3, in whichsaid containerenclosure is a cylindrical can having a longitudinal axis, with anoriginal open end edge border folded re-entrantly inward and flangedtransversely of the axis to define an annular seat; a double-layersandwich seal of insulating material rests on said annular seat; aco-axially disposed current-conductor is supported by and depends fromsaid double-layer seal; and an annular closure element is secured to theeffective outer end of said infolded can, and rests on said seal to holdsaid seal in place for effective sealing action.
 5. A self-controllingelectric cell, as in claim 4, in whichsaid annular closure embodies apressure-responsive element disposed and operative to move topressure-relieving position for the atmosphere within the can, when suchpressure exceeds a predetermined value.
 6. A self-controlling electriccell, as in claim 4, in whichsaid current-conductor embodies asupporting element, and said supporting element is disposed for supportbetween said double-layers of said sandwich seal.
 7. A self-controllingelectric cell, as in claim 6, in whichsaid current conductor has a topouter end that extends upward beyond the top surface of said seal; and acover cap rests on said top outer end of said current conductor to serveas an external electrode of the cell.
 8. A self-controlling electriccell, as in claim 1, in which said container enclosure includes:a. aseal between the inside atmosphere of the container and the outsideambient atmosphere; b. means for holding said seal under closingcompression; and c. said seal-holding means includes atemperature-responsive element, normally rigidly anchored in place tohold said seal in closing compression, and responsive to predeterminedexcess temperature for moving from anchored position to release saidseal to permit said seal to adjust to pressure-relieving position forthe atmosphere within the container.
 9. A self-controlling electriccell, as in claim 8, in whichsaid temperature-responsive element isdisposed to be responsive to the atmospheric temperature developedwithin the cell container.
 10. A self-controlling electric cell, as inclaim 1, in which said container enclosure includes:a. sealing meansbetween the inside atmosphere of the container and the outside ambientatmosphere; b. means responsive to predetermined excess pressure withinsaid container for relieving said pressure at one region of said sealingmeans; and c. means responsive to predetermined excess temperature, -likely to cause explosive rupture of the cell due totemperature-generated pressure, - for relieving said pressure at anotherregion of said sealing means.
 11. A self-controlling electric cell, asin claim 1, in which said container enclosure includes:sealing meansbetween the inside atmosphere of the container and the outside ambientatmosphere; and means separately responsive to predetermined pressure ofatmosphere within said container, or to predetermined temperature of theatmosphere within said container, for selectively controlling saidsealing means to selectively effect easy gradual pressure relief of theinternal atmospheric pressure, or rapid complete pressure relief of theinternal atmospheric cell pressure in said container.
 12. Aself-controlling electric cell, as in claim 3, in whichsaidpressure-responsive element of said seal-holding means consists of anannular ring with individual radial fingers extending radially inward ascantilever elements.
 13. A self-controlling electric cell, as in claim1, in whichone electrode terminal element is disposed as a linearelement co-axially within said container; and said anode means and saidcathode means are respectively in sheet form, both layered mutuallyco-planarly, and together helically wrapped around said co-axial linearelement.
 14. A self-controlling electric cell, as in claim 1, inwhichsaid anode means constitutes a lithium layer on a copper substrate;said cathode means constitutes a carbonaceous cathodic mix layer on analuminum substrate; and said cathode means and said anode means areplanarly layered and separated by a thin sheet of insulating material,to constitute a three-layer composite.
 15. A self-controlling electriccell, as in claim 14, in which said container is elongate about alongitudinal axis;an electrically conductive linear element is axiallysupported along said axis within said container; and said three-layercomposite is helically wrapped around said linear element.
 16. Anelectric cell, as in claim 1, in whichsaid container enclosure has awall that embodies a pressure-distendable part, that has a normalposition while the internal pressure in the cell container enclosure isbelow a predetermined value, and that has a distended position to whichit is moved when said internal pressure exceeds that predeterminedvalue; and said means for preventing aggravation of said undesirablecondition includes a circuit-controlling switch.
 17. An electric cell,as in claim 16, in whichsaid circuit controlling switch includes astationary conducting element and a cooperating movable conductingelement in the electron circuit path of the cell, said movableconducting element being controllable by said distendable part to bemoved to a position where said movable element normally engages saidstationary conducting element, so long as internal atmospheric pressurein said cell is below a predetermined value, and controllable by saiddistendable part to be moved to a separated position to disengage saidstationary conducting element, when said internal pressure in said cellreaches and exceeds said predetermined value.